Single-, dual-, or multiple-stage ferrofluid seals are usefully employed for forming one or more ferrofluid sealing O-rings about a shaft element to provide for sealing of the shaft element. Ferrofluid seals are often useful with bearing assemblies in order to prevent the bearing lubricants from reaching areas that must be free of contamination. Typically such ferrofluid seals used with bearing assemblies are usually exclusion-type seals, that is, they need to withstand typicallya gas pressure difference of only 5-25 inches water per ferrofluid stage.
Bearing assemblies are required in the operation of rotatable shafts, particularly to provide low friction support for rotatable shaft. Generally such bearing assemblies would include radial or thrust bearings, but particularly, radial bearings wherein moveable elements, such as a ball bearing, are retained between inner and outer races by a ball bearing cage. Ferrofluids have been employed in ferrohydrodynamic low-friction ball bearings wherein the rolling element of the ball bearing is suitably magnetized so as to provide a source of magnetic flux to retain the ferrolubricant or ferrofluid within the bearing, such as, for example, as disclosed in U.S. Pat. No. 3,746,407, issued July 17, 1973.
Often bearing assemblies and ferrofluid seal apparatus must be employed where space is at a premium, such as, for example, in small high-speed rotating shafts or spindles, such as in computer disk drives, or textile spindles, or similar operations. Therefore, it is desirable to provide a compact, composite ferrofluid seal and radial bearing assembly wherein the radial bearing assembly provides support for the shaft and the shaft is suitably sealed by an exclusion ferrofluid seal.